Timing first crop alfalfa harvest by calendar date does not work well. Spring climates vary from year to year, and fields managed differently also affects spring regrowth. Different varieties, age of stand, fertility, last season’s cutting schedules, fall harvest or not, can all influence the rate of regrowth in spring. PEAQ, which stands for predictive equation for alfalfa quality, is a quick and easy method to use to assess when individual alfalfa fields are ready for harvest based on a forage quality estimate. All you need is a yard stick and Table 1 in ISU Extension publication CROP 3141, which is available from your county ISU Extension office or download at: https://store.extension.iastate.edu/Product/15234
PEAQ provides a RFV estimate for the standing crop. It is critical that you do not forget to subtract from your standing crop RFV reading in Table 1 by either 15 RFV units for a haylage harvest or 25 RFV units for a hay harvest to account for anticipated forage quality loss from harvest losses that typically occur.
So if you are targeting alfalfa haylage for 150 RFV, you would harvest when Table 1 for PEAQ reads 165 RFV (bud stage alfalfa, stem height 27-28 inches). Typical alfalfa quality targets for cattle are 150 RFV for 1st trimester dairy and calves, 135 RFV for stocker cattle, and 120 RFV for lactating beef cattle.
And, of course, take into account the weather forecasts. Don’t wait for a little more stem growth if it’s going to put you into a rain delay. This spring ISU Extension staff around the state will be providing some PEAQ readings from alfalfa fields and posting them on a website at: https://www.extension.iastate.edu/dairyteam/peaq . You will be able to track these postings over time, but we strongly encourage that you take PEAQ readings from your own alfalfa fields for best assessment of harvest time.